BioMedical Admissions Test (BMAT) Practice Test 2026 - Free BMAT Practice Questions and Study Guide

The initiation of a reflex action begins with the detection of a stimulus by a receptor. Receptors are specialized sensory cells that respond to specific types of stimuli, such as touch, temperature, pain, or pressure. Upon detecting a stimulus, the receptors generate a nerve impulse that travels along sensory neurons to the central nervous system, often directly to the spinal cord.

Once the signal reaches the spine, it may invoke a quick response through a pathway known as a reflex arc, which bypasses the need for higher brain processing, allowing for a rapid, involuntary reaction. This immediate response is vital for survival, as it enables rapid adjustments or actions in response to potentially harmful stimuli without the delay associated with conscious thought processes.

The other options, such as motion of the limbs or thought processes in the brain, do not initiate the reflex action itself; rather, they may occur as a result of the reflex once it has been initiated. Similarly, while hormones can influence behavior and physiological responses, they are not involved in the immediate initiation of a reflex action, making the detection of a stimulus by a receptor the key starting point for the entire reflex process.